Knockout arrangement for presses

ABSTRACT

A vertically reciprocable press slide is provided with knockout pins reciprocably supported by the slide for movement between extended and retracted positions relative thereto. The pins are reciprocated between extended and retracted positions by a lever mechanism which is actuated by a cam mounted on the press frame and a cam follower mounted on the lever mechanism. The cam follower is engaged by the cam during upward movement of the slide to both extend and retract the knockout pins. During downward movement of the slide the cam follower idles relative to the lever mechanism whereby the knockout pins remain in the retracted positions.

[ Apr. 22, 1975 3.364.721 l/l968 Criblczuwmwn 72/345 lU/l972 Keithley et KNOCKOUT ARRANGEMENT FOR PRESSES [75] Inventors: Gordon Berry Freeporti Harry Primary Examiner-Richard J. Herbst E. Keithley, Battle Creek. both of Mich.

Almmey. Agent. or Firm-Meyer, Tilberry & Body [57] ABSTRACT A vertically reciprocable press slide is provided with knockout pins reciprocably supported by the slide for [73] Assignee: Gulf & Western Manufacturing Company (Hastings), Southfield, Mich.

221 Fil d: Feb. 25 197 movement between extended and retracted positions relative thereto. The pins are reciprocated between [21] extended and retracted positions by a lever mecha- Appl. No.: 445,682

nism which is actuated by a cam mounted on the press frame and a cam follower mounted on the lever mech- [52] US. Cl. 72/345 51 Int. B2ld 45/00 amsm- The Cam follflwer engaged by the cam during [58] n w of Search 72/345 2 upward movement of the slide to both extend and retract the knockout pins. During downward movement of the slide the cam follower idles relative to the lever References Cited UNITED STATES PATENTS 72/345 8 Claims, 7 Drawing Figures Hoyt...,....r...

Nita-mums 1878.706

sum 5 0F 6 FIG. 5A

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KNOCKOUT ARRANGEMENT FOR PRESSES The present invention relates to the art of presses and, more particularly. to a knockout arrangement for a press slide.

The reciprocating slide of a metal working press is often provided with a knockout pin or bar arrangement to facilitate displacement of a shaped workpiece from a die component on the slide following the shaping operation. Many knockout arrangements have been provided in the past and generally include knockout components reciprocably supported by the press slide and actuating arrangements by which the knockout components are reciprocated during upward and downward movement of the press slide. Such previous actuating arrangements have provided, for example, for the knockout components to be displaced between the extended and retracted positions thereof twice during a full stroke of the slide. Other actuating arrangements heretofore provided operate to displace the knockout components to the extended positions thereof at a certain point along the path of upward movement of the slide. and provide for the knockout components to be maintained in the extended positions until the slide reaches the same point during downward movement thereof.

It is only necessary that the knockout components be extended for a short period of time during initial upward movement of the slide in order to assure displacement of the workpiece relative to the slide. Accordingly. a second movement of the knockout components between the extended and retracted positions thereof during downward movement of the slide imposes excessive wear on the components which leads to a shorter life thereof and increased maintenance and replacement costs. Maintaining the knockout components in the extended positions thereof during upward and downward movement of the slide is undesirable in that the work area relative to the die component carried by the slide is encumbered with projecting knockout components. Thus. if it is desired to stop the press in order to have access to the die component on the slide the projecting knockout components expose the worker or maintenance personnel to hazardous conditions. Moreover. stresses are imposed on the actuating components by which the knockout components are displaced to the extended positions thereof, and these stresses are applied throughout the upward and downward movement of the slide between the point of knockout component actuation. Such prolonged application of stresses to the components shortens the expected life thereof and leads to undue wear which increases maintenance and replacement costs. Moreover, down time of the press for such maintenance or replacement operations results in a loss of production.

in accordance with the present invention, a knockout arrangement is provided which avoids the disadvantages of knockout arrangements heretofore provided including the disadvantages specifically enumerated above. In this respect, the knockout arrangement of the present invention provides for the knockout components to be both extended and retracted only during initial upward movement of the slide. Accordingly, a workpiece knockout function is achieved and the knockout components then remain in the retracted position throughout the remainder of the upward movement of the slide and through the total downward movement of the slide. Therefore, the knockout components are actuated momentarily and just once during the total stroke of the slide. it will be appreciated. therefore. that wear of the component parts of the knockout mechanism is minimized as is the application of stresses thereto during a total stroke of the slide. Accordingly, extended life for the component parts is achieved together with a reduction in replacement, rcpair and maintenance costs and an increase in useful production time for the press.

In accordance with a preferred embodiment of the invention, actuation of the knockout components is achieved through a cam and cam follower arrangement between the slide and the frame of the press. Momentary actuation ofthe knockout components is provided for by a unique structural interengagement between the cam follower and a lever mechanism by which the knockout components are mechanically displaced relative to the slide. More particularly, during upward movement of the press slide the cam follower engages the cam on the press frame to displace the lever mechanism and thus the knockout components from the retracted to the extended positions thereof and then back to the retracted positions. The knockout components then remain in the retracted positions during the remainder of the upward movement of the slide. During downward movement of the slide the cam follower engages the cam in an idling or bypassing movement which is ineffective to displace the lever mechanism. whereby the knockout components remain in the retracted positions during the total downward movement of the slide.

it is an outstanding object of the present invention to provide a knockout arrangement for the reciprocating slide of a press and in which the knockout components are momentarily extended only during upward movement of the slide following a work performing operation.

Another object is the provision of a knockout arrangement for presses by which a reduction in wear of component parts of the arrangement is realized A further object is the provision of a knockout arrangement for presses in which the period of imposition of stresses on the component parts of the arrangement during a stroke of the press slide is minimized.

Still another object is the provision of a knockout arrangement of the foregoing character in which the press slide and frame are provided with coopcrable interengaging actuating components which are operable only during upward movement of the slide to achieve knockout component displacement.

Yet another object is the provision of an improved cam operated knockout arrangement for presses.

Still a further object is the provision of a cam operated knockout arrangement for presses including a unique cam and cam follower assembly in which the cam follower is operable during upward movement of the press slide to achieve knockout component displacement relative to the slide and is rendered inoperable during downward movement of the slide.

Yet a further object is the provision of a cam operated knockout arrangement for presses which is simple and reliable in operation.

The foregoing objects and others will in part be obvi' ous and in part pointed out more fully hereinafter in conjunction with the written description of a preferred embodiment of the invention illustrated in the accompanying drawings in which:

FIG. 1 is a side elevation view of a press having a knockout arrangement in accordance with the present invention incorporated therein;

FIG. 2 is a plan view. partially in section. looking in the direction of line 2-2 in FIG. 1;

FIG. 3 is an elevation view looking in the direction of line 3-3 in FIG. 2;

FIG. 4 is a sectional elevation view looking along line 44 in FIG. 2;

FIG. 5 is a sectional elevation view along line 5---S in FIG. 2 and illustrating the component parts of the knockout assembly in the positions thereof just prior to displacement of the knockout pins during upward movement of the slide;

FIG. 5A is a sectional elevation view similar to FIG. 5 and illustrating the component parts in the positions thereof to extend the knockout pins; and.

FIG. 5B is a sectional elevation view similar to FIG. 5 and illustrating the component parts in the positions thereof during a portion of the downward movement of the slide.

Referring now in greater detail to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting the invention. FIG. 1 shows a press comprised of a frame A which supports a slide assembly including a slide member B for reciprocating movement upwardly and downwardly relative to the press bed C. As is well known. press bed C is shaped to support a die component D which is suitably mounted thereon. and slide member B is adapted to support a cooperable die component E which is suitably mounted thereon. The slide assembly is interconnected with an eccentric F by a coupling G. and eccentric F is driven by a motor H through a flywheel .l. which motor and flywheel are interconnected by a suitable drive belt K. As is well known. flywheel J is rotated by a motor H to rotate eccentric F. whereby slide B and die component E. thereon are vertically reciprocated relative to die component D to perform work on a workpiece interposed therebetwecn.

As seen in FIGS. 1 and 2, press frame A includes four upstanding corner posts each provided with a corre sponding guide I2 for slide B. Suitable gibbing 14 is in terposed between guides 12 and slide B for guiding reciprocating movement of the slide relative to the press frame. In the embodiment illustrated, press slide B includes a lower slide component 16 which supports a knockout pin assembly M and a pin actuating lever mechanism N as described more fully hereinafter. Further, frame posts 10 defining the rear side of the press are provided with an adjustable cam assembly P described more fully hereinafter and which is cooper-able with lever mechanism N to reciprocate knockout pin assembly M during upward movement of press slide B.

Referring now to FlGS. 2-5, it will be seen that knockout pin arrangement M includes a pair ofcircular knockout pins 18 which are rigidly interconnected in parallel spaced apart relationship by a support bar 20. Pins 18 can be interconnected with bar 20 in any desired manner and such as by threaded studs 22 having their opposite ends disposed in corresponding threaded bores provided in pins 18 and bar 20. Pins 18 are disposed generally centrally between the front and back sides of the slide member 16 and extend downwardly through corresponding openings 24 provided therefor in slide member 16. Pins 18 and bar 20 are adapted to reciprocate vertically relative to slide member 16 and, in this respect, the slide member is provided with a vertical support rod 26 having its lower end 28 rigidly secured to slide member 16 such as by threaded fasteners 30. Rod 26 extends upwardly through a corresponding opening 32 in slide member 16 and through a corresponding opening 34 provided therefor in cross bar 20. A compression spring 36 surrounds rod 26, and the upper end of spring 36 is enclosed within an inverted cup-shaped retainer 40'having its lower end rigidly sccured to cross bar 20 such as by welding. It will be appreciated therefore that cross bar 20 and pins 18 are biased upwardly relative to slide member 16 by spring 36 and are displaceable downwardly relative to slide member 16 against the bias of spring 36. When bar 20 is in its uppermost position relative to slide member 16, pins 18 are in a retracted position relative to the slide member and. accordingly. the pins are displaced to the extended positions thereofin response to displacement of bar 20 downwardly toward slide member 16. The upper end of rod 26 is threaded to receive nuts or the like 42 which limit upward displact cant of pins 18 and bar 20 by spring 36, and the top sides 7 bar 20 are pro vided with wear plates 44 which o I'llQ pins 18 for the purpose set forth hereinafter.

Knockout pins 18 are normally disposed in the retracted positions thereof relative to slide member 16 and are adapted to be displaced to the extended positions thereof by pin actuating lever mechanism N. Lever mechanism N includes a first lever 46 which is generally L-shaped and is mounted on slide B for oscillating movement about a horizontal axis 48 extending between the sides of the press frame. In the embodi mcnt illustrated. lever 46 includes a hub 50 pivotally supported by a pin 52 having its opposite ends suitably secured to a pair of support arms 54 having base portions 56 bolted or otherwise secured to an upright sup port plate 58 of slide B. Lever 46 further includes a center arm 60 extending radially from hub 50 and suitably secured thercto such as by welding. and a pair of side arms 62 on opposite sides of arm 60 and likewise secured to hub 50, such by welding. Each of the arms 62 extends through a corresponding window 64 in slide plate 58 and has a nose end 66 engaging wear plate 44 overlying a corresponding one of the knockout pins 18. It will be seen, therefore, that pivotal movement of lever 46 counterclockwise in FIG. 5 operates to displace knockout pins 18 downwardly relative to slide member 16 against the bias of pin return spring 36.

Lever mechanism N further includes a second lever 68 mounted on slide B for oscillating movement about horizontal axis '70 which is parallel to and spaced above axis 48 of lever 46. More particularly, lever 68 includes a pivot pin 72 rigidly supported by a pair of pin support. arms 74 mounted on a base plate 76 which in turn is bolted or otherwise secured to an upright support plate 78 of press slide B. Lever 68 includes a pair of legs 80 and 82 which are apertured to receive a corresponding end of pin 72 whereby lever 68 is pivotal relative to pin 72. Lever 68 further includes a plate portion 84 integral with legs 80 and 82. and having a nose portion 86 on the end and side thereof corresponding to leg 80, and a side portion 88 on the end and side thereof corresponding to leg 82. Nose portion 86 is provided with a wear plate 90 engaging nose portion 92 of lever arm 60 of lever 46, whereby pivotal movement of lever 68 clockwise in FIG. 5 imparts counterclockwise pivotal movement to lever 46.

End 88 of plate portion 84 of lever 68 is provided with a flat abutment shoulder 94 for the purpose set forth hereinafter, and a cam lever 96 is mounted on lever 68 for pivotal movement about a horizontal axis 98 which is parallel to and spaced below axis of lever 68. More particularly. cam lever 96 includes a pin shaft 100 extending through opening 102 in plate por tion 84 of lever 68 and having its free end provided with a suitable split retaining ring or the like 104 to re tain the pin shaft and thus lever 96 in place with respect to lever 68. Cam lever 96 includes a flat bottom face 106 adapted to engage shoulder 94 of lever 68 to limit clockwise pivotal movement of cam lever 96 relative to lever 68 as viewed in FIG. 5. Engagement between cam lever surface 106 and shoulder 94 defines a neutral position for cam lever 96 relative to lever 68, and it will be seen that cam lever 96 is adapted to freely pivot counterclockwise in H6. 5 relative to lever 68 and that clockwise pivotal movement of cam lever 96 when in the neutral position relative to lever 68 imparts clockwise pivotal movement to lever 68. it will be further seen in FIG. 5 that the bias of spring 36 on the knockout pin arrangement biases lever 68 counterclockwise about axis 70. Accordingly, leg 82 of lever 68 is provided with an adjustable stop screw 108 adapted to en gage mounting plate 76 to limit counterclockwise pivotal movement of lever 68.

Cam mechanism P includes a cam assembly 110 mounted on the press frame and a cam follower ele ment 112 mounted on cam lever 96. Cam follower 112 is in the form of a roller mounted on lever 76 for rotation about an axis 114 parallel to and spaced from lever axes 70 and 98. Cam follower 112 cooperates with the cam assembly as set forth more fully hereinafter to achieve the desired reciprocating movement of the knockout pins during slide operation.

Cam assembly 110 includes a support plate 116 extending horizontally between rear frame posts 10 of the press frame. The opposite ends of plate 116 are suitably secured to the corresponding frame posts 10 such as by threaded fasteners 118. Further, plate 116 is provided with a plurality of horizontally extending reinforcing ribs 120 which are welded or otherwise secured thereto. A cam mounting block 122 is rigidly secured to support plate 116 such as by welding, and mounting block 122 adjustably supports a cam support block 124. In this respect, support block 124 is provided with an elongated T-shaped recess 126 adapted to receive the heads of threaded fasteners 128, the shanks of which fasteners extend through corresponding openings 130 in mounting block 122 and are provided on their outer ends with corresponding nuts 132. Accordingly, it will be appreciated that cam support block 124 is adapted to be vertically adjusted relative to support plate 116. To facilitate vertical adjustment of the cam support block relative to support plate 116, support block 124 is provided with an elongated adjustment rod 134. The upper end of rod 134 is threaded and extends slidably through an opening 135 in block 124. The rod is attached to block 124 by nuts 136 and 138, and the lower end of the rod is threadedly secured to the top of mounting block 122. Thus, by loosening nuts 132 to release support block 124, nuts 136 and 138 can be ad justed relative to rod 134 to move cam support block 124 upwardly or downwardly relative to mounting block 122. The purpose of this adjustment is set forth more fully hereinafter.

As seen in FIG. 2. cam support block 124 is provided with an outwardly extending mounting plate 140 to which a cam member 142 is suitably secured. such as by threaded fasteners 144. Cam 142 is provided with a vertically extending cam way 146 which. as best seen in FIG. 5, is defined by spaced apart cam surfaces 148 and 150 which are adapted to receive cam follower 112 therebetween. Cam surfaces 148 and 150 are spaced apart equidistant along the entire vertical length of the cam and the spacing therebetween corresponds generally to the diameter of cam follower 112 and provides for the follower to have rolling contact with the cam surfaces. Cam surface 148 is the primary cam surface engaged by follower 112 and includes. sequentially from the lower end thereof toward the upper end. a vertical portion 148a. a first inclined portion l48h ex tending upwardly and inwardly toward the press slide. a short vertical portion 148('. an inclined portion 148d extending upwardly and outwardly of the press slide. and a vertically extending portion 1486.

The cooperative interengagement between the cam and follower components and the resulting actuation of the knockout pins is illustrated in FIGS. 5, 5A and 5B. in this respect. when the components are in the positions thereof illustrated in FIG. 5 and the press slide is moving upwardly relative to the press frame immediately following a work forming operation. knockout pins 118 are in the retracted positions thereof and are maintained retracted by the bias of spring 36. As the press slide moves upwardly. cam follower 112 first en gages inclined cam surface 148]). whereby cam follower lever 96 is biased to pivot clockwise about axis 98. Engagement of cam lever surface 106 with shoulder 94 of lever 68 prevents relative pivotal movement be tween earn lever 96 and lever 68 in the clockwise direction. Accordingly. cam lever 96 and lever 68 pivot together in the clockwise direction about axis 70 of lever 68. Such clockwise pivotal movement of lever 68 im parts counterclockwise movement to lever 46 about axis 48 thereof. whereby nose 66 of lever arms 62 push bar 20 and thus knockout pins 18 downwardly relative to slide member 16.

When cam follower 112 reaches cam surface 148C. as illustrated in FIG, 5A. knockout pins 118 are fully extended. Upon continued upward movement of the slide, cam follower 112 engages cam surface 148:! and the bias of knockout pin spring 36 moves the knockout pins upwardly relative to slide member 16 toward the retracted positions thereof. At the same time. the bias of spring 36 pivots lever 46 clockwise about axis 48 thereof and nose 92 of lever arms 60 bias lever 68 and cam lever 96 counterclockwise about axis 70 of lever 68. When cam follower 112 reaches cam surface 1480 the knockout pins are fully retracted and remain retracted during the remainder of the upward movement of the slide relative to the frame.

During downward movement of the slide cam follower 112 rolls along surface 148e and then engages inclined cam surface 148d. Engagement of the cam follower with the latter surfaee biases the cam follower lever 96 to pivot counterclockwise about axis 98. Such latter pivotal movement is relative to lever 68, whereby the follower moves in an idling relationship along cam surfaces 148d and 1480. as illustrated in FIG. SB. without imparting any displacement to lever 68. When cam follower [12 passes cam surface 148C it pivots clockwise about axis 98 under the influence of gravity and to the extent permitted by surface 106 of cam follower lever 96 and shoulder 94 of lever 68. Thus, the levers are again positioned as illustrated in FIG. of the drawing. When so positioned the components of the assembly are prepared to displace knockout pins l8 from the retracted positions thereof during the subequent upward movement of the slide.

It will be appreciated from the foregoing description that the knockout pins are momentarily moved from the retracted to the extended positions thereof during upward movement of the slide and are then displaced back to the retracted positions and remain therein during the remainder of the upward movement of the slide and during the total downward movement of the slide. The adjustment of cam 142 provided for by the adjustable cam support block 124 and adjusting rod 134 facilitates adjusting the location along the path of upward mm ement of the slide at which cam follower 112 engages cam surface [48b to initiate dispiacemerit of the knockout pins from the retracted toward the extended positions thereof.

While considerable emphasis has been placed herein on a specific knockout pin structure and lever and cam actuating arrangements. it will be appreciated that many changes can be made in the preferred structure without departing from the principles of the present invention. In this respect, the knockout components can be other than pin elements and could, for example, be defined by a bar or bars extending across the lower face of the slide member for displacement relative thereto by pin elements similar to knockout pins 18. Likewise, many lever arrangements or modifications of the lever arrangement disclosed herein can be devised to achieve displacement of the knockout pins relative to the slide member. Further, many structural embodiments of cam and cam follower components couid be devised to provide the desired bypass relationship between the cam and cam follower during downward movement of the slide to avoid knockout pin displacement during such slide movement. As many possible embodiments of the present invention may be made and as many possible changes may be made in the embodiment herein illustrated and described, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation.

What is claimed is:

1. A knockout arrangement for a press having a frame and a slide supported by said frame for reciproeating movement upwardly and downwardly for performing work on workpieces comprising, knockout pin means supported by said slide for reciprocating movement between extended and retracted positions relative thereto, a first lever mounted on said slide for oscillating movement between first and second positions about a first axis and having an end spaced from said first axis, a second lever having opposite ends and mounted on said slide for oscillating movement about a second axis intermediate said opposite ends, said opposite ends of said second lever interengaging one with said pin means and the other with said end of said first lever, whereby a cycle of oscillation of said first lever from said first position to said second position and back to said first position respectively extends and retracts said pin means, said slide and frame carrying cam and follower means cooperably interengaging to displace said first lever through a cycle of oscillation only during upward movement of said slide, said cam and follower means including cam means on said frame and follower means on said first lever, said follower means including a third lever mounted on said first lever for pivotal movement relative thereto about a third axis, and shoulder means interengaging said first and third levers in a first relative position and for pivotai movement together in one direction about said first axis from said relative position, said third lever being pivotal relative to said first lever in the opposite direction about said first axis from said relative position, said cam follower means engaging said cam means to pivot said third lever in said one and opposite directions respectively during upward and downward movement of said slide.

2. The knockout arrangement according to claim 1, wherein said cam means is adjustably mounted on said frame for adjusting the location along the path of upward movement of the slide at which said follower element is engaged to pivot said first and third levers about said first axis.

3. The knockout arrangement according to claim 1, and spring means biasing said pin means toward the retracted positions thereof.

4. The knockout arrangement according to claim 1, wherein said third lever has an end spaced from said third axis, and a cam follower roller on said end of said third lever and engaging said cam means.

5. A knockout arrangement for a press having a frame and a slide supported by said frame for reciprocating movement upwardly and downwardly for performing work on workpieces comprising, knockout means supported by said slide for reciprocating movement between extended and retracted positions relative thereto, lever means pivotally mounted on said slide for oscillating movement between first and second positions, said lever means having opposite ends, one of said opposite ends of said lever means interengaging with said knockout means, whereby a cycle of oscillation of said lever means from said first position to said second position and back to said first position respectively extends and retracts said knockout means, pivotal cam follower means on said slide having a neutral position engaging the other of said opposite ends of said lever means and being pivotal in opposite directions to first and second positions relative to said neutral position, said follower means being pivotal between said neutral and first positions thereof to displace said lever means through said cycle and being pivotal between said neutral and second positions thereof in idling relationship with respect to said lever means, and cam means on said frame interengaging with said cam follower means to pivot said cam follower means between said neutral and first positions thereof during upward movement of said slide and between said neutral and second positions thereof during downward movement of said slide.

6. The knockout arrangement according to claim 5, wherein said lever means includes a first lever mounted on said slide for pivotal movement about a first axis and having an end spaced from said axis, and a second lever having first and second ends and mounted on said slide for pivotal movement about a second axis intermediate said first and second ends, said first end interengaging with said knockout means and said second end interengaging with said end of said first lever, said cam foltracted position thereof.

8. The knockout arrangement according to claim 7, wherein said cam means is adjustably mounted on said frame to provide for adjusting the point of operative displacement of said cam follower means along the path of upward movement of said slide. 

1. A knockout arrangement for a press having a frame and a slide supported by said frame for reciprocating movement upwardly and downwardly for performing work on workpieces comprising, knockout pin means supported by said slide for reciprocating movement between extended and retracted positions relative thereto, a first lever mounted on said slide for oscillating movement between first and second positions about a first axis and having an end spaced from said first axis, a second lever having opposite ends and mounted on said slide for oscillating movement about a second axis intermediate said opposite ends, said opposite ends of said second lever interengaging one with said pin means and the other with said end of said first lever, whereby a cycle of oscillation of said first lever from said first position to said second position and back to said first position respectively extends and retracts said pin means, said slide and frame carrying cam and follower means cooperably interengaging to displace said first lever through a cycle of oscillation only during upward movement of said slide, said cam and follower means including cam means on said frame and follower means on said first lever, said follower means including a third lever mounted on said first lever for pivotal movement relative thereto about a third axis, and shoulder means interengaging said first and third levers in a first relative position and for pivotal movement together in one direction about said first axis from said relative position, said third lever being pivotal relative to said first lever in the opposite direction about said first axis from said relative position, said cam follower means engaging said cam means to pivot said third lever in said one and opposite directions respectively during upward and downward movement of said slide.
 1. A knockout arrangement for a press having a frame and a slide supported by said frame for reciprocating movement upwardly and downwardly for performing work on workpieces comprising, knockout pin means supported by said slide for reciprocating movement between extended and retracted positions relative thereto, a first lever mounted on said slide for oscillating movement between first and second positions about a first axis and having an end spaced from said first axis, a second lever having opposite ends and mounted on said slide for oscillating movement about a second axis intermediate said opposite ends, said opposite ends of said second lever interengaging one with said pin means and the other with said end of said first lever, whereby a cycle of oscillation of said first lever from said first position to said second position and back to said first position respectively extends and retracts said pin means, said slide and frame carrying cam and follower means cooperably interengaging to displace said first lever through a cycle of oscillation only during upward movement of said slide, said cam and follower means including cam means on said frame and follower means on said first lever, said follower means including a third lever mounted on said first lever for pivotal movement relative thereto about a third axis, and shoulder means interengaging said first and third levers in a first relative position and for pivotal movement together in one direction about said first axis from said relative position, said third lever being pivotal relative to said first lever in the opposite direction about said first axis from said relative position, said cam follower means engaging said cam means to pivot said third lever in said one and opposite directions respectively during upward and downward movement of said slide.
 2. The knockout arrangement according to claim 1, wherein said cam means is adjustably mounted on said frame for adjusting the location along the path of upward movement of the slide at which said follower element is engaged to pivot said first and third levers about said first axis.
 3. The knockout arrangement according to claim 1, and spring means biasing said pin means toward the retracted positions thereof.
 4. The knockout arrangement according to claim 1, wherein said third lever has an end spaced from said third axis, and a cam follower roller on said end of said third lever and engaging said cam means.
 5. A knockout arrangement for a press having a frame and a slide supported by said frame for reciprocating movement upwardly and downwardly for performing work on workpieces comprising, knockout means supported by said slide for reciprocating movement between extended and retracted positions relative thereto, lever means pivotally mounted on said slide for oscillating movement between first and second positions, said lever means having opposite ends, one of said opposite ends of said lever means interengaging with said knockout means, whereby a cycle of oscillation of said lever means from said first position to said second position and back to said first position respectively extends and retracts said knockout means, pivotal cam follower means on said slide having a neutral position engaging the other of said opposite ends of said lever means and being pivotal in opposite directions to first and second positions relative to said neutral position, said follower means being pivotal between said neutral and first positions thereof to displace said lever means through said cycle and being pivotal between said neutral and sEcond positions thereof in idling relationship with respect to said lever means, and cam means on said frame interengaging with said cam follower means to pivot said cam follower means between said neutral and first positions thereof during upward movement of said slide and between said neutral and second positions thereof during downward movement of said slide.
 6. The knockout arrangement according to claim 5, wherein said lever means includes a first lever mounted on said slide for pivotal movement about a first axis and having an end spaced from said axis, and a second lever having first and second ends and mounted on said slide for pivotal movement about a second axis intermediate said first and second ends, said first end interengaging with said knockout means and said second end interengaging with said end of said first lever, said cam follower means including a third lever pivotally mounted on said first lever at a third axis spaced from said first axis, and means interengaging said first and third levers to pivot together about said first axis during said pivotal movement of said follower means between said neutral and first positions thereof.
 7. The knockout arrangement according to claim 6, and means biasing said knockout means toward said retracted position thereof. 